- A
The VOICE class traffic is always sent before other classes, but if it exceeds 30% of the interface bandwidth, excess traffic is dropped.
Priority queuing sends traffic first; the percent 30 sets a policer that drops excess traffic beyond 30%.
- B
The VOICE class traffic is always sent before other classes, and excess traffic beyond 30% is queued in the default class.
Why wrong: Priority traffic is not re-queued; excess is dropped unless police is configured differently.
- C
The VIDEO class traffic is treated with strict priority after the VOICE class.
Why wrong: Only the class with the priority command gets strict priority; VIDEO uses bandwidth guarantee.
- D
The class-default uses Weighted Fair Queuing with a maximum queue size of 100 packets, and all classes share the remaining bandwidth equally.
Why wrong: The class-default uses fair-queue, but the bandwidth allocation for VIDEO is fixed at 20%, not equally shared.
Quick Answer
The answer is that excess traffic from the VOICE class is dropped when it exceeds 30% of the interface bandwidth. This occurs because the priority percent command enables strict priority queuing, which guarantees that VOICE traffic is always transmitted before any other class, but it also applies an implicit policer at the configured percentage. Any traffic beyond that 30% threshold is immediately dropped rather than queued, preventing starvation of lower-priority queues like VIDEO or class-default. On the ENCOR 350-401 exam, this tests your understanding of the critical distinction between policing and shaping in priority queues—a common trap is assuming excess priority traffic is buffered or re-queued. Remember the key rule: priority percent means “send first, but drop the excess.” A useful memory tip is “Priority is a police, not a queue”—if it exceeds the percent, it’s gone, not stored.
350-401 QoS Architecture Practice Question
This 350-401 practice question tests your understanding of qos architecture. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Consider the following configuration snippet:
policy-map QOS_POLICY
class VOICE
priority percent 30
class VIDEO
bandwidth percent 20 queue-limit 50 packets
class class-default
fair-queue queue-limit 100 packets
What is the effect of this configuration?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The VOICE class traffic is always sent before other classes, but if it exceeds 30% of the interface bandwidth, excess traffic is dropped.
The 'priority percent 30' command under the VOICE class enables strict priority queuing, meaning VOICE traffic is always transmitted before any other class. However, the priority queue is policed at 30% of the interface bandwidth; any traffic exceeding this rate is dropped, not queued. This is a fundamental behavior of the priority command in Cisco IOS — excess priority traffic is dropped to prevent starvation of other queues.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The VOICE class traffic is always sent before other classes, but if it exceeds 30% of the interface bandwidth, excess traffic is dropped.
Why this is correct
Priority queuing sends traffic first; the percent 30 sets a policer that drops excess traffic beyond 30%.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The VOICE class traffic is always sent before other classes, and excess traffic beyond 30% is queued in the default class.
Why it's wrong here
Priority traffic is not re-queued; excess is dropped unless police is configured differently.
- ✗
The VIDEO class traffic is treated with strict priority after the VOICE class.
Why it's wrong here
Only the class with the priority command gets strict priority; VIDEO uses bandwidth guarantee.
- ✗
The class-default uses Weighted Fair Queuing with a maximum queue size of 100 packets, and all classes share the remaining bandwidth equally.
Why it's wrong here
The class-default uses fair-queue, but the bandwidth allocation for VIDEO is fixed at 20%, not equally shared.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that excess priority traffic is re-queued into the default class or another queue, when in fact it is always dropped to enforce the bandwidth limit and protect other traffic classes.
Trap categories for this question
Command / output trap
Only the class with the priority command gets strict priority; VIDEO uses bandwidth guarantee.
Detailed technical explanation
How to think about this question
Under the hood, the priority command creates a low-latency queue (LLQ) that is serviced first by the scheduler. The policer is a token-bucket mechanism that drops packets exceeding the configured rate to protect other queues from starvation. In real-world deployments, this is critical for voice traffic (e.g., VoIP RTP streams) where jitter and delay must be minimized, but the policer prevents a single flow from monopolizing the link.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 350-401 question test?
QoS Architecture — This question tests QoS Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The VOICE class traffic is always sent before other classes, but if it exceeds 30% of the interface bandwidth, excess traffic is dropped. — The 'priority percent 30' command under the VOICE class enables strict priority queuing, meaning VOICE traffic is always transmitted before any other class. However, the priority queue is policed at 30% of the interface bandwidth; any traffic exceeding this rate is dropped, not queued. This is a fundamental behavior of the priority command in Cisco IOS — excess priority traffic is dropped to prevent starvation of other queues.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 24, 2026
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